Integrated illumination assembly for symbology reader

ABSTRACT

Systems and methods provide an illumination assembly for a mark reader. A light transmitter is arranged in a surrounding relationship to an interior area, with the light transmitter having a proximal end and a distal end. An illumination source provides a light for transmission into the light transmitter. The light transmitter distal end allows the light from within the light transmitter to pass through and out of the distal end to provide bright field illumination and dark field illumination. The light transmitter distal end may include a first portion and a second portion, where light from within the light transmitter passes through and out of the first portion to provide bright field illumination, and light from within the light transmitter passes through and out of the second portion to provide dark field illumination.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/683,622, filed Apr. 10, 2015, and entitled “Integrated IlluminationAssembly for Symbology Reader” (the “Preceding Priority Application”),which is hereby incorporated by reference.

The Preceding Priority application is a continuation-in-part of pendingU.S. patent application Ser. No. 14/278,504, filed May 15, 2014, andentitled “Method and Apparatus for Providing Omnidirectional Lighting ina Scanning Device,” which is a continuation of U.S. patent applicationSer. No. 13/623,344, filed Sep. 20, 2012, now U.S. Pat. No. 8,740,078dated Jun. 3, 2014, and entitled “Method and Apparatus for ProvidingOmnidirectional Lighting in a Scanning Device,” which is a continuationof U.S. patent application Ser. No. 13/294,285, filed Nov. 11, 2011, nowU.S. Pat. No. 8,282,000 dated Oct. 9, 2012, and entitled “Method andApparatus for Providing Omnidirectional Lighting in a Scanning Device,”which is a continuation of U.S. patent application Ser. No. 12/552,107filed Sep. 1, 2009, now U.S. Pat. No. 8,061,613 dated Nov. 22, 2011, andentitled “Method and Apparatus for Providing Omnidirectional Lighting ina Scanning Device,” which is a continuation of U.S. patent applicationSer. No. 10/911,989 filed Aug. 5, 2004, now U.S. Pat. No. 7,604,174dated Oct. 20, 2009, and entitled “Method and Apparatus for ProvidingOmnidirectional Lighting in a Scanning Device,” which is acontinuation-in-part of U.S. patent application Ser. No. 10/693,626filed Oct. 24, 2003, now U.S. Pat. No. 7,823,783 dated Nov. 2, 2010, andentitled “Light Pipe Illumination System and Method,” each of which arehereby incorporated by reference.

The Preceding Priority application is a continuation-in-part of pendingU.S. patent application Ser. No. 14/316,906, filed Jun. 27, 2014, andentitled “Light Pipe Illumination System and Method,” which is acontinuation of U.S. patent application Ser. No. 13/623,336, filed Sep.20, 2012, now U.S. Pat. No. 8,770,483 dated Jul. 8, 2014, and entitled“Light Pipe Illumination System and Method,” which is a continuation ofU.S. patent application Ser. No. 13/294,286, filed Nov. 11, 2011, nowU.S. Pat. No. 8,342,405 dated Jan. 1, 2013, and entitled “Light PipeIllumination System and Method,” which is a continuation of U.S. patentapplication Ser. No. 12/900,593 filed Oct. 8, 2010, now U.S. Pat. No.8,061,614 dated Nov. 22, 2011, and entitled “Light Pipe IlluminationSystem and Method,” which is a continuation of U.S. patent applicationSer. No. 10/693,626 filed Oct. 24, 2003, now U.S. Pat. No. 7,823,783dated Nov. 2, 2010, and entitled “Light Pipe Illumination System andMethod,” each of which are hereby incorporated by reference.

The Preceding Priority application is a continuation-in-part of pendingU.S. patent application Ser. No. 14/183,766, filed Feb. 19, 2014, andentitled “Low Profile Illumination for Direct Part Mark Readers,” whichis a continuation of U.S. patent application Ser. No. 12/900,605 filedOct. 8, 2010, now U.S. Pat. No. 8,672,227 dated Mar. 18, 2014, andentitled “Low Profile Illumination for Direct Part Mark Readers,” whichis a continuation of U.S. patent application Ser. No. 11/019,763 filedDec. 21, 2004, now U.S. Pat. No. 7,823,789 dated Nov. 2, 2010, andentitled “Low Profile Illumination for Direct Part Mark Readers,” eachof which are hereby incorporated by reference.

The Preceding Priority application is a continuation-in-part of pendingU.S. patent application Ser. No. 12/900,617 filed Oct. 8, 2010, andentitled “Integrated Illumination Assembly for Symbology Reader,” whichis a continuation of U.S. patent application Ser. No. 11/257,411 filedOct. 24, 2005, now U.S. Pat. No. 7,874,487 dated Jan. 25, 2011, and alsoentitled “Integrated Illumination Assembly for Symbology Reader,” bothof which are hereby incorporated by reference.

STATEMENT CONCERNING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

FIELD OF THE TECHNOLOGY

This technology relates to machine vision systems and symbology readersthat employ machine vision and more particularly to illuminators for thesame.

BACKGROUND OF THE TECHNOLOGY

Machine vision systems use image acquisition devices that include camerasensors to deliver information on a viewed subject. The system theninterprets this information according to a variety of algorithms toperform a programmed decision-making and/or identification function. Foran image to be most-effectively acquired by a sensor in the visible, andnear-visible light range, the subject should be properly illuminated.

In the example of symbology reading (also commonly termed “barcode”scanning) using an image sensor, proper illumination is highlydesirable. Symbology reading entails the aiming of an image acquisitionsensor (CMOS camera, CCD, etc.) at a location on an object that containsa symbol (a “barcode”), and acquiring an image of that symbol. Thesymbol contains a set of predetermined patterns that represent anordered group of characters or shapes from which an attached dataprocessor (for example, a microcomputer) can derive useful informationabout the object (e.g. its serial number, type, model, price, etc.).Symbols/barcodes are available in a variety of shapes and sizes. Two ofthe most commonly employed symbol types used in marking and identifyingobjects are the so-called one-dimensional barcode, consisting of a lineof vertical stripes of varying width and spacing, and the so-calledtwo-dimensional barcode consisting of a two-dimensional array of dots orrectangles.

By way of background FIG. 1 shows an exemplary scanning system 100adapted for handheld operation. An exemplary handheld scanning applianceor handpiece 102 is provided. It includes a grip section 104 and a bodysection 106. An image formation system 151, shown in phantom, can becontrolled and can direct image data to an on-board embedded processor109. This processor can include a scanning software application 113 bywhich lighting is controlled, images are acquired and image data isinterpreted into usable information (for example, alphanumeric stringsderived from the symbols (such as the depicted two-dimensional barcodeimage 195). The decoded information can be directed via a cable 111 to aPC or other data storage device 112 having (for example) a display 114,keyboard 116 and mouse 118, where it can be stored and furthermanipulated using an appropriate application 121. Alternatively, thecable 111 can be directly connected to an interface in the scanningappliance and an appropriate interface in the computer 112. In this casethe computer-based application 121 performs various imageinterpretation/decoding and lighting control functions as needed. Theprecise arrangement of the handheld scanning appliance with respect toan embedded processor, computer or other processor is highly variable.For example, a wireless interconnect can be provided in which no cable111 is present. Likewise, the depicted microcomputer can be substitutedwith another processing device, including an onboard processor or aminiaturized processing unit such as a personal digital assistant orother small-scale computing device.

The scanning application 113 can be adapted to respond to inputs fromthe scanning appliance 102. For example, when the operator toggles atrigger 122 on the hand held scanning appliance 102, an internal cameraimage sensor (that is part of the image formation system 151) acquiresan image of a region of interest 131 on an object 105. The exemplaryregion of interest includes a two-dimensional symbol 195 that can beused to identify the object 105. Identification and other processingfunctions are carried out by the scanning application 113, based uponimage data transmitted from the hand held scanning appliance 102 to theprocessor 109. A visual indicator 141 can be illuminated by signals fromthe processor 109 to indicate a successful read and decode of the symbol195.

In reading symbology or other subjects of interest, the type ofillumination employed is of concern. Where symbology and/or other viewedsubjects are printed on a flat surface with contrasting ink or paint, adiffuse, high-angle “bright field” illumination may best highlight thesefeatures for the sensor. By high-angle it is meant, generally, lightthat strikes the subject nearly perpendicularly (normal) or at an anglethat is typically no more than about 45 degrees from perpendicular(normal) to the surface of the item being scanned. Such illumination issubject to substantial reflection back toward the sensor. By way ofexample, barcodes and other subjects requiring mainly bright fieldillumination may be present on a printed label adhered to an item orcontainer, or on a printed field in a relatively smooth area of item orcontainer.

Conversely, where a symbology or other subject is formed on amore-irregular surface, or is created by etching or peening a patterndirectly on the surface, the use of highly reflective bright fieldillumination may be inappropriate. A peened/etched surface hastwo-dimensional properties that tend to scatter bright fieldillumination, thereby obscuring the acquired image. Where a viewedsubject has such decidedly two-dimensional surface texture, it may bebest illuminated with dark field illumination. This is an illuminationwith a characteristic low angle (approximately 45 degrees or less, forexample) with respect to the surface of the subject (i.e. an angle ofmore than approximately 45 degrees with respect to normal). Using suchlow-angle, dark field illumination, two-dimensional surface texture iscontrasted more effectively (with indents appearing as bright spots andthe surroundings as shadow) for better image acquisition.

In other instances of applied symbology a diffuse direct illuminationmay be preferred. Such illumination is typically produced using adirect-projected illumination source (e.g. light emitting diodes (LEDs))that passes through a diffuser to generate the desired illuminationeffect.

To take full advantage of the versatility of a camera image sensor, itis desirable to provide bright field, dark field and diffuseillumination. However, dark field illumination must be presented closeto a subject to attain the low incidence angle thereto. Conversely,bright field illumination is better produced at a relative distance toensure full area illumination.

Commonly assigned U.S. patent application Ser. No. 11/014,478, entitledHAND HELD SYMBOLOGY READER ILLUMINATION DIFFUSER and U.S. patentapplication Ser. No. 11/019,763, entitled LOW PROFILE ILLUMINATION FORDIRECT PART MARK READERS, both by Laurens W. Nunnink, the teachings ofwhich are expressly incorporated herein by reference, provide techniquesfor improving the transmission of bright field (high angle) and darkfield (low angle) illumination. These techniques include the provisionof particular geometric arrangements of direct, bright field LEDs andconical and/or flat diffusers that are placed between bright fieldilluminators and the subject to better spread the bright field light.The above-incorporated HAND HELD SYMBOLOGY READER ILLUMINATION DIFFUSERfurther teaches the use of particular colors for improving theillumination applicable to certain types of surfaces. Often, the choiceof bright field, dark field, direct or diffuse light is not intuitive touser for many types of surfaces and/or the particular angles at whichthe reader is directed toward them. In other words, a surface may appearto be best read using dark field illumination, but in practice, brightfield is preferred for picking out needed details, especially at acertain viewing angle. Likewise, with handheld readers, the viewingangle is never quite the same from surface to surface (part-to-part) andsome viewing angles be better served by bright field while other may bebetter served by dark field. The above-referenced patent applicationscontemplate the application of a plurality of illumination types toachieve the best image for a particular surface and viewing angle.

It has been recognized that handheld readers pose a number of uniqueconcerns. At least some of these concerns are shared in relation tofixed readers. For example, the material from which most light pipes areconstructed is acrylic (commonly termed “plexiglass”). Acrylic exhibitsa high refractive index (approximately 1.58), which is well suited forinternal transmission of light down a light pipe. However, acrylic tendsto shatter easily in response to impact. This may limit the life andendurance of a handheld reader (particularly a cordless/wireless model)that is expected to occasionally drop and strike a hard floor, perhapsagainst the light pipe. While the light pipe could be armored withcushioning and external housings, this undesirably increases productioncosts, weight, obtrusiveness and may optically obscure the pipe.

Moreover, the light pipes described in the above referenced patents mayinclude a chamfered end to project dark field illumination via internalreflection. Refraction through the polished chamfered end also generatesdirect bright field illumination. The optical clarity of the light pipeand end tends to create a spotlight effect, in which each individualillumination source (red LEDs, for example) is clearly visible oncertain surfaces (see FIG. 7 below). This controverts the typical goalof providing an even spread of illumination.

Also, where a conical diffuser is employed to provide an overall sourceof direct diffuse illumination, prior art devices are limited in theirability to spread light from a few individual illumination sources(LEDs, for example) throughout the diffuser surface, and then onto thesubject as diffuse light. Thus, the diffuse light tends to exhibit acharacteristic, localized light spot and dark spot effect. Addingfurther illumination sources to the diffuse section may be limited bothby space and the relative cost of illumination sources, particularlywhere relatively costly blue-colored LEDs are employed.

Further, prior art readers often include visual indicators located attheir back, top or another surface that denote the current status of thereader (for example, power on/off, good read, error, bad read, ready,not-ready, etc.). Various information can be presented to the user viadifferent color lights (red/green, for example) and/or via blinkingpatterns. However, in a production environment, small, rear-mounted ortop-mounted indicators may be overlooked or present a distraction whilethe user tries to focus on the surface being read. A technique formore-conveniently integrating indicators with the user's main point ofinterest is highly desirable.

SUMMARY OF THE TECHNOLOGY

This technology overcomes the disadvantages of the prior art byproviding a plurality of novel features that can be applied variously toa reader to improve the illumination performance in both darkfield/direct bright field and direct diffuse types of illumination.Further features allow for increased light pipe durability withoutincreasing weight or size and better readability of status indicators byplacing such indicators in proximity to the subject and significantlyenlarging to overall size of the indicator.

In one embodiment, the light pipe is constructed from durablepolycarbonate for increased shock resistance. The chamfered end of thelight pipe is textured or frosted to further diffuse refracted lightpassing through the end so as to present a more even effect. Theconical/tapered diffuser within the light pipe is illuminated by areflector with a white textured surface that reflects a plurality ofrearward-directed (opposite the illumination and viewing direction)illumination sources back into the diffuser. The reflector can define apredetermined cross section that directs further light into theforwardmost, remote regions of the diffuser to generate a better overallspread of light and alleviate light and dark spotting effects. Thetextured surface on the chamfered light pipe end can be employed tobetter project indicator light. The textured surface can alternatively(or in addition) be applied to the exposed portion of the inner walladjacent to the distal (forward) end of the pipe.

The illumination sources are arranged in a ring at or near the inner endof the light pipe, and can be multi-colored sources that respond to thecontroller to project and appropriate color and/or blink in anappropriate pattern to indicate various conditions, such as read successor failure. Typically the controller is adapted to provide thesespecialized indications between actual image acquisition, so that theimage acquisition is properly illuminated. The controller can operateindividual portions of the ring so that only corresponding portions ofthe light pipe perimeter are illuminated in a particular color(quadrants, for example) at a given time. Different quadrants may besimultaneously illuminated in different colors in one example.

In an illustrative embodiment, the light pipe defines a polygonal (forexample rectangular) cross section (with the polygon being generallydefined as at least four linear or non-linear sides, joined at corners(that may be rounded) to form a (typically) non-equilateral shape. Thechamfered edge on each side is at a fixed angle and thus the differinglength of the North-South versus East-West sides (in the case of arectangle), generates two different distances for convergence of darkfield rays, which increases depth of field. Stated differently, thepolygon (rectangle) includes at least two pairs of opposing sides andthe first pair of opposing sides has a length different than the secondpair of opposing sides to generate two differing-distance convergencepoints for dark field rays.

In an alternative embodiment, a mark reader comprises a lighttransmitter arranged in a surrounding relationship to an interior area,the light transmitter having a proximal end and a distal end. Anillumination source is adapted to provide a light for transmission intothe light transmitter. The light transmitter distal end includes a firstportion and a second portion, the first portion being adapted to allow aportion of the light from within the light transmitter to pass throughand out of the distal end to provide bright field illumination, and thesecond portion being adapted to internally reflect and redirect adifferent portion of the light to exit at or near the distal end toprovide dark field illumination.

In an additional alternative embodiment, a light transmitting assemblyfor illuminating a mark that is imaged by an image sensor comprises alight transmitter arranged in a surrounding relationship to an interiorarea, the light transmitter having a proximal end and a distal end. Anillumination source is adapted to provide a light for transmission intothe light transmitter. The light transmitter distal end includes achamfered surface and a diffusive surface, the diffusive surface beingadapted to allow a first portion of the light from within the lighttransmitter to pass through and out of the diffusive surface to providebright field illumination, and the chamfered surface being adapted tointernally reflect and redirect a second portion of the light so the atleast a different portion of the light exits the distal end to providedark field illumination.

In yet an additional alternative embodiment, an illumination assemblyfor a mark reader comprises a light transmitter arranged in asurrounding relationship to an interior area, the light transmitterhaving an internal wall, an external wall, a proximal end, and a distalend. An illumination source is adapted to provide a light fortransmission into the light transmitter. The light transmitter distalend is adapted to allow at least a portion of the light from within thelight transmitter to pass through and out of the distal end to providebright field illumination, and the distal end being adapted tointernally reflect and redirect a different portion of the light so thedifferent portion of the light exits the interior wall to provide darkfield illumination.

In yet an additional alternative embodiment, an illumination assemblyfor a mark reader comprises a light transmitter arranged in asurrounding relationship to an interior area, the light transmitterhaving an internal wall, an external wall, a proximal end, and a distalend. An illumination source is adapted to provide a light fortransmission into the light transmitter. The light transmitter distalend comprises a first flat surface and a second flat surface differentthan the first flat surface, the first flat surface adapted to allow aportion of the light from within the light transmitter to pass throughand out of the distal end to provide bright field illumination, and thesecond flat surface adapted to allow a different portion of the light topass through and out of the distal end to provide dark fieldillumination.

In still an additional alternative embodiment, an illumination assemblyfor a mark reader comprises a light transmitter arranged in asurrounding relationship to an interior area, the light transmitterhaving a proximal end and a distal end. An illumination source isadapted to provide a light for transmission into the light transmitter.The light transmitter distal end is adapted to allow the light fromwithin the light transmitter to pass through and out of the distal endto provide bright field illumination, and the light transmitter distalend is adapted to allow the light from within the light transmitter topass through and out of the distal end to provide dark fieldillumination.

In still an additional alternative embodiment, a method for providingbright field illumination and dark field illumination comprisesproviding a light transmitter arranged in a surrounding relationship toan interior area, the light transmitter having a proximal end and adistal end; providing an illumination source for providing a light fortransmission into the light transmitter; allowing the light from withinthe light transmitter to pass through and out of the distal end forproviding bright field illumination; and allowing the light from withinthe light transmitter to pass through and out of the distal end forproviding dark field illumination.

In yet still an additional alternative embodiment, a method comprisesproviding a light transmitter and arranging the light transmitter in asurrounding relationship to an interior area, the light transmitterhaving a proximal end and a distal end; providing an illumination sourceand arranging the illumination source for providing a light fortransmission into the light transmitter; and using a first portion and asecond portion of the light transmitter distal end, the first portionallowing a portion of the light from within the light transmitter topass through and out of the distal end for providing bright fieldillumination, and the second portion internally reflecting andredirecting a different portion of the light to exit near the distal endfor providing dark field illumination.

In yet still an additional alternative embodiment, an illuminationassembly for a mark reader disposed along an optical viewing axiscomprises a light pipe defined by at least four sides including at leasta first opposing pair of sides and a second opposing pair of sides. Thelight pipe includes a chamfered edge at a distal end that directs lightfrom a light source at the proximal end through the chamfered edge ontoa surface as dark field light rays. The convergence distance of the darkfield light rays for the at least first opposing pair of sides is lessthan the convergence distance of the dark field light rays for the atleast second opposing pair of sides.

In yet still an additional alternative embodiment, an illuminationassembly for a mark reader disposed along an optical viewing axiscomprises a rectangular light pipe defined by a set of linear ornon-linear sides that intersect at each of four corners that cause theapproximate direction of two adjacent sides to vary by substantiallyninety degrees. A light source is at a proximal end of the rectangularlight pipe to direct light through a distal end of the rectangular lightpipe onto a surface as dark field light rays. The dark field light raysfrom the set of linear or non-linear sides that intersect at each offour corners converge at at least two differing distance ranges of thedark field light rays onto the surface.

The foregoing and other objects and advantages of the technology willappear in the detailed description which follows. In the description,reference is made to the accompanying drawings which illustrate apreferred embodiment of the technology.

BRIEF DESCRIPTION OF THE DRAWINGS

The technology description below refers to the accompanying drawings, ofwhich:

FIG. 1, already described, is a perspective view of a handheld scanningsystem with integrated illumination according to the prior art;

FIG. 2 is a side cross section of a handheld scanning system that can beemployed in connection with the teachings of this technology;

FIG. 3 is a front view of the scanning system of FIG. 2;

FIG. 4 is an exploded view of the illumination assembly and image sensorfor the scanning system of FIG. 2;

FIG. 5 is a somewhat schematic side cross section of the sensor andilluminator assembly for use with the scanning system of FIG. 2detailing the path taken by various illumination types;

FIG. 6 is a somewhat schematic side cross section of the light pipe ofthe illuminator assembly of FIG. 5 more particularly showing theprojection of direct bright field illumination;

FIG. 7 is a diagram showing an illumination effect in which individualillumination sources are projected onto a surface through a polishedchamfered light pipe end;

FIG. 8 is a fragmentary perspective view of the viewing end of thereader featuring the illumination assembly and having a textured surfaceon the chamfered light pipe end;

FIG. 9 is a diagram showing an illumination effect achieved on a surfaceemploying a textured chamfered light pipe end in accordance with anembodiment of this technology;

FIG. 10 is a block diagram of the image processor and illuminationcontrol circuitry interacting with the sensor, trigger and illuminationring, featuring individual quadrant control and multi-color illuminationsources;

FIG. 11 is a fragmentary perspective view of the viewing end of thereader showing the textured chamfered light pipe end illuminated in redas an indicator;

FIG. 12 is a fragmentary perspective view of the viewing end of thereader showing the textured chamfered light pipe end illuminated ingreen as an indicator;

FIG. 13 is a fragmentary perspective view of the viewing end of thereader showing the textured chamfered light pipe end illuminated in redin predetermined quadrants and green in other predetermined quadrants asan indicator;

FIG. 14 is a schematic side cross section of the, light pipe, diffuser,illumination sources and reflector showing a predetermined reflectorgeometry so as to increase projection of light along remote regions ofthe diffuser;

FIG. 15 is a somewhat schematic side cross section of the light pipe ofthe illuminator assembly detailing the draft angle provided to allowmolding of the light pipe and showing an alternative placement of thediffusive surface at the distal end of the light pipe;

FIG. 16 is a schematic diagram of a generalized shape for a rectangularcross section light pipe featuring representations of a North, South,East and West edge;

FIG. 17 is a schematic representation of the convergence of dark fieldrays from the North and South edges of the light pipe of FIG. 16 showinga first distance thereto;

FIG. 18 is a schematic representation of the convergence of dark fieldrays from the East and West edges of the light pipe of FIG. 16 showing afirst distance thereto;

FIG. 19 is an exposed perspective view of a light pipe according to analternate embodiment of this technology defining an elliptical crosssection;

FIGS. 20-30 are schematic side cross sections of a portion of a lightpipe of the illuminator assembly showing alternative configurations ofthe distal end of the light pipe; and

FIG. 31 is an end view of a light pipe of the illuminator assemblyshowing an alternative configuration of the distal end of the lightpipe.

DETAILED DESCRIPTION OF AN ILLUSTRATIVE EMBODIMENT

FIG. 2 shows a cross sectional side view of an illustrative embodimentof the reader 200 according to the present technology. The imager 212and an illumination board 214 are positioned on a shock-resistantmounting (not shown) within the housing 206. In this exemplaryembodiment, the processor module and related functional electroniccomponents are mounted on a processor board 215. The grip portion 202and the trigger 204 are functionally cooperative with the housing 206and components of the processor board 215. The grip portion 206 includesa conveniently placed trigger 204 that can be actuated by a finger ofthe user to initiate the image acquisition and decoding function. Moreparticularly, pressing the trigger causes all types and colors ofillumination (as described further below) to be simultaneously projectedonto the subject of interest, and also causes corresponding acquisitionof an image by the imager.

With brief reference to the illuminator, the illumination board 214supports a plurality of LEDs 310 that are red in this embodiment (avariety of colors can be used). The LEDs 310 are directed forwardly,toward the opening of the reader. These LEDs are positioned behind apassive light pipe 244 that internally transmits light from the ring ofLEDs 310 to a front end 230. In this embodiment, the front end 230includes a chamfered surface 232. Various examples of a light pipe foruse with a reader or similar application are shown and described in U.S.patent application Ser. No. 10/693,626, entitled LIGHT PIPE ILLUMINATIONSYSTEM AND METHOD, by William H. Equitz, et al., the teachings of whichare expressly incorporated herein by reference.

Briefly explained, light passes through the extended body of the lighttransmitter, e.g., light pipe 244, from the sides and/or inner end,adjacent to the LEDs 310. The body is formed from atransmissive/transparent substance. As discussed above, one concern forthe light pipe is durability and impact resistance. In an embodiment ofthis technology, the light pipe is constructed from transparentpolycarbonate (available under the trade name Makrolon from BASF ofGermany, or alternatively Lexan® available from the General ElectricCompany). This substance can be injection-molded using a liquid resinthat is formed into a desired shape as discussed further below. Thetransmitted light is reflected internally by the angled/chamferedsurface 232 of the light pipe 244 to exit at a low angle toward thecenter optical axis 270. While acrylic displays a superior refractiveindex (approximately 1.58), it has been recognized that the refractiveindex of polycarbonate (approximately 1.49) is sufficient to achieve thedegree of light transmission and internal reflection employed for darkfield illumination in accordance with embodiments of this technology.All or portions of the inner and/or outer wall surfaces of the lightpipe 244 can be coated with opaque paint or another compound to preventleakage of light into or out of the pipe. In this example, a shield 250is also provided along the inner surface of the light pipe. One functionof the shield 250 is to prevent transmission of diffuse light (describedbelow) in to the light pipe. Another function is to redirect lighttransmitted from the reflector (see below) back into the diffuser.

In this example, the ring of LEDs 310 acts to produce a red directbright field effect along with the dark field effect through refractionof some light from the LEDs through the chamfered surface 232. Ingeneral, at short reading distances from a surface (<25 mm between thelight pipe distal (forward) end 230 and surface), the bright fieldillumination from the light pipe 230 tends not to interfere with thedark field illumination. The bright field illumination is available,however, for larger reading distances (>25 mm between the end 230 andthe surface). This is useful for easy-to-read codes, such asblack-and-white printed labels. In alternate embodiments, a separatebright field illuminator can be provided, and as described below. Infact, many available imagers include integral red bright fieldilluminators. In an alternate embodiment, a separate bright fieldilluminator can be provided in a discrete color, such as green.

Note that a pair of aiming LEDs 220 (typically emitting green light) areprovided. However, these are optional. Such aiming LEDs may be integralwith the commercially available image employed herein.

A tether cord 260 provides electrical power to the reader 200, as wellas a communication transmission path for the decoded character string ofthe encoded information, though it is contemplated that the reader 200can be configured with battery power and wireless communication forcomplete portable flexibility.

With reference also to FIG. 3, a front view of the reader 200 is shown.The distribution and placement of the individual LEDs (or otherappropriate light elements) 310 that transmit light to the light pipe244 is represented by a series of adjacent Xs positioned around theperimeter of the light pipe 244 in line with the distal end 230. Theillustrative LED placement creates a generally uniform lighting effect.The placement of these light elements and others used herein is highlyvariable. In addition, the addressing of light elements can becontrolled so that only certain elements are activated at certain timesto create the desired overall dark field illumination intensity and/orbias (e.g. lighter on one side than another) to the dark fieldillumination effect on the subject. This variable-addressing feature isdescribed further below and is discussed in further detail in theabove-incorporated U.S. patent applications and in other commonlyassigned U.S. patent applications referenced therein.

Reference is now also made to the exploded view of FIG. 4, which furtherdetails the components of the overall illuminator assembly with respectto the imager 212. As 10 shown, the various illuminator assemblycomponents, described above have been separated to reveal individualstructural details. The imager 212 resides at the left side of the view.The illumination board assembly 214 is located ahead of it. Placed infront of the illumination board 214 and LEDs 310 is the proximal (orbase) end 410 of the light pipe 244, which receives transmitted lightfrom the LEDs 310, and internally transmits it to the chamfered distalend 230. The LEDs 310, or other light elements, may also be placed totransmit light into the light pipe 244 through an exterior wall and/oran interior wall of the light pipe. A tapered (also loosely termed“conical”) diffuser 280 (refer also to FIG. 2) is nested within thelight pipe 244, with a narrowed proximal opening 420 provided adjacentto the imager 212 and a widened distal opening 422 located at theopposing end. In an illustrative embodiment, this diffuser 280 can beconstructed from a thin (1-3 millimeter) polymer material with afrosted/textured interior. As noted above, a thin shield 250 is providedagainst the interior of the light pipe to block the diffuser'stransmitted light from entering the light pipe 244. In this manner, thelight emitted from the diffuser does not mix with the light pipe'stransmission.

Space may be limited in the region between the shield 250 and the innersurface of the diffuser 280. Moreover, it is contemplated in variousembodiments to provide a blue color for the diffuse illumination,employing high-output, blue-colored LEDs, which are more costly than thered or green versions. Thus, use of a smaller number of such LEDs ishighly desirable. The fewer individual illumination sources employed,the greater the need to spread the light around the diffuser so as toavoid a light and dark spotting effect on the surface of interest. Toaccomplish the desired spread of diffuse illumination with a minimalnumber of individual illumination sources, the light projected by thediffuser is provided by a set of (four) rearward-projecting LEDs 282mounted on the illumination board 214 on a side opposite the ring oflight pipe LEDs 310. These LEDs 282 project rearward into a conical,spherical, parabolic (or other shape) reflector 290 that spreads thereflected light throughout the inner surface of the diffuser 280 so thatit exits as a substantially uniform spread of direct, diffuse light ontothe surface of interest. As will be described further below, thereflector's shape can be optimized to improve the spread of light alongthe conical diffuser. In this embodiment, the reflector 290 isconstructed from polymer with a white textured surface to furtherdiffuse the light reflected therefrom. This indirect projection of lightwith a diffusing reflective surface significantly aids in reducing thenumber of diffuse illumination LEDs 282 employed to project the diffuseillumination, thereby reducing production costs and power consumption.As noted above, in this embodiment, the diffuse illumination LEDs 282are high-output blue LEDs. However, the particular colors used for eachtype of illumination are highly variable. However, it is highlydesirable that the diffuse illumination be spaced apart on the spectrumsufficiently from the dark field illumination to allow adequateresolution of the two wavelengths of light.

A translucent “conical” filter 292 is provided. The filter 292 isadapted to filter out light with larger wavelengths, thereby allowingsmaller wavelength blue light to pass out of the diffuser and onto thesurface, but preventing the retransmission of any reflected red lightfrom the surface, which would otherwise tend to become retransmitted asdiffuse red light along with the red dark field illumination. Thewavelength spread between red light and blue light is sufficient toaccomplish this filtering without compromising the performance of eithertype (dark field/direct bright field versus direct diffuse) ofillumination. The filter 292 conforms to the shape of the diffuser'souter (exposed) surface, and can be snapped or adhered onto the diffusersurface using a variety of fastening techniques that should be clear tothose of ordinary skill. Note that instead of a separate filter (292), asimilar effect can be obtained through the use of a colored diffuser(see FIG. 6 below). The color should be selected so that the diffusertransmits the diffuse light (blue in this embodiment), but does notreflect the dark field light (red in this embodiment) transmitted fromthe light pipe.

Thus, to summarize, at least two discrete sets of illuminationtransmitters (LEDs, for example) are provided according to theillustrative embodiment, the direct diffuse transmitters 282 and thedark field transmitters 310. In accordance with the illustrativeembodiment, each discrete set of transmitters 282 and 310 generates acorresponding discrete illumination color. For example, direct diffuseillumination can be generated by blue LEDs and dark field (and directbright field) can be generated by red LEDs. The use of two discretecolors allows each type of illumination to be restricted to itsparticular application, without mixing, using filtering within theillumination assembly. In this embodiment, each type of illuminationcreates an image that is received by the imager 212. The imager in thisembodiment includes a conventional monochrome sensor that produces agrayscale image from the colored light. Note in alternate embodiments acolor sensor can be employed. One such implementation is shown anddescribed in commonly assigned U.S. patent application entitled SYSTEMAND METHOD FOR EMPLOYING COLOR ILLUMINATION AND COLOR FILTRATION IN ASYMBOLOGY READER by Laurens W. Nunnink, and filed on even date herewith,the teachings of which are expressly incorporated herein by reference.

Reference is now made to FIGS. 5 and 6, which describe generally theillumination patterns achieved by the light pipe 244 and diffuser 280 ofthe illumination assembly. Referring first to FIG. 5, a cross section ofan implementation of the diffuser 280 is shown, with light pipe 244 asdescribed generally above, relative to the imager assembly 212 (andassociated lens structure 240). Dark field illumination (rays 510) isdirected into the light pipe 244 that is internally reflected at thechamfered distal (forward) end 230 to be, thus, directed at the objectsurface 520 at a low angle. Further information regarding the basicdesign and implementation of passive light pipes with selectivelyactuated illumination to provide dark field illumination can be found inthe above-incorporated U.S. patent application Ser. No. 10/693,626,entitled LIGHT PIPE ILLUMINATION SYSTEM AND METHOD, by William H.Equitz, et al. Direct illumination (rays 532) from blue LEDs 282 isconverted into totally diffuse direct illumination by reflection off thereflector 290, and passage into and through the diffuser 280 of thisembodiment. The diffuser 280 thereby projects diffuse illumination onthe object surface 520 within the field of view, depicted as the regiondefined by dashed lines 540. In this embodiment the diffuser 280 is,itself, translucent, without a color tint or color-filtering effect. Inalternate embodiments, the diffuser can be tinted to generate a desiredcolor and/or act as a filter (using colored or white illuminationsources (282)). It should be noted that the diffuser 280 according tothis embodiment, and other embodiments described herein, can beconstructed and arranged so as to be removably attached to the hand heldscanning appliance. In one example, the diffuser can be removed to allowthe transmitters 282 to operate as non-diffuse direct bright fieldillumination. Alternatively, the diffuser can be provided with movableshutters that selectively expose clear (non-frosted/non-diffusing)windows in the overall diffuser. The removability of the diffuser 280can be achieved by incorporating snap-fit clearances and/or features inthe diffuser and light pipe 244 that permit removable assembly (notshown).

In this embodiment direct non-diffuse bright field illumination (seerays 620 in FIG. 6) is provided by refraction of light through thechamfered end 230 of the light pipe 244. As shown particularly in FIG.6, a portion of the light internally reflected along the pipe 244 exitsdirectly from the chamfered end 230 as relatively high-angle (usuallygreater than 45 degrees relative to the surface 520) bright field light(rays 620). The remaining light is internally reflected by the chamferedend 230 to exit adjacent to the inner corner 630 of the pipe 244 asdiscussed generally above. Note that the light pipe can be modified inalternate embodiments to include a flattened ring (residing in a planeperpendicular to the optical axis 270. This would permit additionalbright field light to be directly transmitted onto the surface 520.Likewise, a nested light pipe with a flat (unchamfered) ring formed atits distal end can be used in alternate embodiments for directtransmission of bright field light along a waveguide separate from thedepicted dark field light pipe 244. This can be useful whereilluminators having a discrete color are used for direct bright fieldlight. Alternatively, where optional direct bright field transmittersare employed they can be located so as to project light throughclear/transparent portions (not shown) of the diffuser 280.

While not shown in this illustration for simplicity, it can be assumedthat a filter (292 above) may be applied over the diffuser to preventmigration of reflected dark field (and bright field) light into thediffuser 280.

As discussed in the above Background of the Technology, illuminatorlight pipes according to various prior implementations of mark readersinclude a polished distal end. Referring briefly to FIG. 7, an image 710acquired of a reflective surface using a light pipe with a polished endis shown. This image 710 clearly depicts delineated spots 720 producedby the individual illumination sources in the illumination ring. Thesespots lead to a somewhat broken illumination pattern that may effectacquisition of the mark 730.

Referring to FIG. 8, the reader 200 is fitted with an illuminationassembly 800 that includes a light pipe 810 according to an embodimentof this technology. The light pipe 810 includes a chamfered end 820about its forward perimeter having a general size and shape as describedabove. Notably, the depicted outer surface 830 of the chamfered end 820is finely frosted or textured. This provides a mild diffusive effect tolight exiting as direct bright field illumination (see FIG. 6) and alsoto internally reflected light exiting as dark field illumination. Theresulting diffusion generates the image shown in FIG. 9.

Note that the ring of light 920 surrounding the mark 930 is more uniformand the mark, itself, appears better contrasted than the results of thepolished-end version shown in FIG. 7.

The frosted or textured surface 830 provided along the chamfered endfacilitates a novel and desirable display of reader status according toan embodiment of this technology. Before describing the status displayin detail, reference is made to FIG. 10, which schematically describesthe basic components of the illumination and image processing system ofthe reader. The circuit board (215 in FIG. 2) of the reader includes aprocessor and illumination controller, shown schematically asprocessor/control block 1010. The processor/control 1010 can employconventional image processing and mark-recognition/decoding processes.The processor/control 1010 receives signals from the trigger (block1012), which are used to operate the illumination assembly and to obtainimage date via the imager (block 1014). The aiming LEDs (block 1016 andsee also 220 in FIG. 2) are operated before and during image acquisitionunder control of the processor 1010. These serve to keep the user aimedat the mark during the acquisition process, particularly where the scanis performed at a standoff distance from the object surface. To thisend, it is noted that acquisition of the image according to thisembodiment involves a stepping through of a plurality of illuminationtypes (dark field and diffuse) in timed sequence, with associated imageacquisition of the mark during each type of illumination. Typically thebest image (or a combination of the images) is chosen to decode the datarepresented by the mark. Before acquisition, and after acquisition, thereader may indicate a variety of status codes, such as ready-to-read,read successful, read unsuccessful, etc. These indicators are describedfurther below.

During the stepping process, the processor 1010 directs the illuminationring (block 1020) to illuminate. It then directs the diffuse illuminator(block 1018) to illuminate. As described in various of theabove-incorporated-by-reference patent applications, the ring 1020 caninclude individual banks of LEDs (or other illumination sources) that,in this example, are formed into quadrants—namely top/north 1022,bottom/south 1024, right/east 1026 and left/west 1028 (as viewed fromoutside, toward the reader front). These quadrants can be individuallyaddressed by the processor. This allows the output of each quadrant tobe varied so as to generate the desired effect on the object. This isparticularly useful, where the reader may be disposed at anon-perpendicular angle to the object surface or the surface isnon-flat. Various automatic adjustment processes can be included toefficiently cycle through various lighting arrangements among thequadrants to determine the arrangement/profile that achieves the bestimage. In this embodiment, the individual illumination sources (LEDs1030) are commercially available multi-color LEDs (red and green in thisembodiment, denoted schematically by the split line down the middle ofeach LED 1030), capable of projecting either of two colors in responseto the processor 1010. This can be useful, from an imaging standpoint,where a different color is to be provided for dark field and directbright field. More significantly, the illumination ring's multicolorcapability allows the light pipe (particularly the frosted end 820) toproject a highly visible, subject-adjacent indicator light in aplurality of colors.

FIG. 11 details generally the illumination of the light pipe 810 for thepurpose of providing the user an indicator. In this example, the fourquadrants 1110, 1120, 1130 and 1140 of the textured chamfered edge 820are illuminated red (denoted by the encircled R's) by their appropriatebanks of LEDs in the ring. The frosted surface in fact generates abright, diffuse color strip that enhances viewing of the indicator. Thisindicator can be illuminated before, during or after image acquisitionas a continuous or blinking signal. Blinks can be timed in the manner ofMorse code to achieve a desired status message. It should be clear thatproviding a large, clearly visible indicator light at the distal end ofthe light pipe (near to the mark—where the user will have his or herattention focused) affords a highly effective indicator that does notdistract the user from the subject at hand and that is visible whetherthe reader is placed in close proximity to the object surface or at astandoff therefrom. In fact, at standoff distance, the indicator itselfprojects a colored light onto the surface, further focusing the user'sattention on the task at hand.

As shown in FIG. 12, all light-pipe-end quadrants 1110, 1120, 1130, 1140are illuminated in green (denoted by the encircled G's). This can be asolid (continuously green) or blinking indicator. It can also blinkalternatively with red (or another color) according to any predeterminedpattern to provide a particular message.

As shown in FIG. 13, the indicator is characterized by two (or more)simultaneous colors displayed by different quadrants (or other sections)of the light pipe edge. In this example, the top quadrant 1110 is redand the left quadrant 1140 is green. The opposed bottom and leftquadrants 1120 and 1130, respectively, may also be red and green. Thispattern may blink, or alternate (e.g. red and green switch). Likewise, aunique rolling change of colors may occur in which each quadrant, inturn changes to a different color so that the color change appears tomigrate around the perimeter. Any observable and desirable shift ofcolors is contemplated as an indicator according to this technology.

Reference is now made to FIG. 14, which shows a variation of theabove-described reflector shape. As discussed above, the length andangle (A) of the conical diffuser 280 (typically less than 45 degreeswith respect to the axis 270 in each quadrant) defines a remote, distalregion 1410 between the interior wall of the diffuser 280 and the shield250 that is small in volume and difficult for light from the reflector1420 to fill adequately. The gap between the inner perimeter of theillumination board 214 and the interior wall of the diffuser furtherobscures transmission of light into this remote region 1410. Thus, thereflecting surface 1422 of the reflector 1420 of this embodimentincludes a plurality of steps 1424, 1426, 1428, 1429 which are designedto direct specific portions of the reflected light (rays 1430) from theLEDs 282 toward the various parts of the diffuser, including the remoteregions 1410. Not that, adjacent to the central window 1450 in thereflector (through which the imager views the subject), the plurality ofsmall, angled steps 1429 formed in the cross section are particularlyadapted to transmit rays 1430 from the light sources 282 to variouspoints along the remote region 1410 for an optimized spread of lightalong the entire diffuser surface. The reflector 1420 in this embodimentalso includes a textured surface and a white surface color for maximumdiffusion. In alternate embodiments, a different surface color andsurface finish can be employed. In this manner a more-uniformillumination of the complete diffuser surface is achieved, and thepresence of light and dark spotting on the object is minimized.

While a stepped reflector 1420 is shown and described according to anembodiment of this technology, it is expressly contemplated thatreflectors having a variety of surface cross-sectional profiles can beemployed in alternate embodiments. Such reflectors should be adapted,using optical-focusing techniques, to spread light along the length of atapered or conical diffuser of a shape generally contemplated herein soas to avoid undesirable spotting on localized regions of the surface ofinterest.

It is contemplated that a light pipe with a textured or frostedchamfered end according to the various embodiments of this technologycan be produced by a variety of techniques including grit blasting orpeening of a finished surface, a desirable construction techniqueentails molding of the light pipe from poured resin. The chamfered endis located near the bottom of the mold and the rearward end (adjacent tothe illumination ring) is located at the top of the mold, at whichlocation the finished pipe is ejected from the mold. The bottom of themold is provided with a frosted or textured pattern so as to form thissurface effect on the chamfered end of the finished pipe. Referring toFIG. 15 which shows the cross section of the light pipe 244 the mold isconstructed with a slight draft angle that tapers, so that the resultinglight pipe 244 defines a pair of inner walls having a draft angle ADtherebetween of approximately at least 2 degrees (each side being 1degree relative to the axis 270). Because the mold includes afrosted/textured surface, the draft angle is set at approximately 2degrees, rather than the typical 1 degree for a smooth molded part. This2-degree draft angle better overcomes the possible adhesion effectscreated between the finished pipe and the textured mold surface. Thisdraft angle is employed where the texture is applied to the chamferedends 230. Note that the chamfered ends 230 each define therebetween anangle of approximately 70 degrees (each end being approximately 35degrees relative to the axis 270). It should be clear, however, that thetechniques used for forming the light pipe and other components hereincan vary within the scope of ordinary skill.

Referring further to FIG. 15, according to an alternate embodiment, thefrosted or textured finish can be applied to the inner wall of the lightpipe 244 at the end location 1520. This location 1520 is exposed beyondthe distal end of the diffuser 280 and shield 250 described above toallow unobstructed passage of dark field light (rays 510). This causesthe reflected dark field light to pass through a diffusive structureprior to striking the mark surface. Note that the textured surface canalso be applied to the outer side (location 820) in an embodiment of thetechnology. Alternatively, the textured surface may be selectivelyapplied to only one of the inner location (1520) or outer location (820)as appropriate. It should be noted that, when applying texture to theinterior wall at location 1520, the draft angle AD (FIG. 15) wouldtypically be greater than 2 degrees. An appropriate draft angle can bedetermined by those of skill in the molding plastic parts.

According to the embodiments described above, the general crosssectional perimeter shape of the light pipe is rectangular (taken on aplane through axis 270). For the purposes of this description, the term“rectangular” shall include minor deviations of the sides of therectangle from a straight-line geometry. In other words, a rectangularshape herein may include, for example, curvilinear arcs as shown anddescribed. In general, the term rectangular shall be defined generallyas a set of linear or non-linear sides that intersect at each of fourcorners (that may be significantly rounded corners) that cause theapproximate direction of two adjacent sides to vary by approximatelyninety degrees. A highly generalized representation of a rectangularlight pipe 1610 is shown in FIG. 16. As described above, the sides 1620,1622, 1624 and 1626 of the rectangular light pipe 1610 can be defined interms of North (arrow N), South (arrow S), East (arrow E) and West(arrow W). Likewise, each edge of the distal, chamfered end can becorrespondingly represented as EN (edge North), ES (edge South), EE(edge East) and EW (edge West). The length LNS between the North edge ENand South edge ES is shorter (in this embodiment) that the length LEWbetween the East edge EE and West edge EW (LNS<LEW). Note that inalternate embodiments the reverse may be true (LNS>LEW) or is thesemeasurements can be approximately equal.

Referring to FIGS. 17 and 18, the chamfered edge along each side isdisposed at the same fixed angle (approximately 55 degrees in thisembodiment), generating dark field light rays that converge at point1710 at an average fixed angle .theta. of approximately 32 degrees(representing half the chamfer angle along with an induced draft angleof 1 degree and further refraction as the light exits the pipe interiorwall). Since the distance LNS is less than the distance LEW, theconvergence distance of light DNS for the pair of opposing sides EN andES is less than the convergence distance DEW of light from the pair ofopposing sides EE and EW. Thus this arrangement affords a wider depth offield for the reader by providing two differing distance ranges ofillumination for the mark. In an embodiment of this technology theapproximate length NS is 3 cm, the approximate length EW is 4.5 cm. DNSis approximately 0.92 cm, while DEW is approximately 1.23 cm. Thus adesirable difference of more than 0.31 cm is provided for greater depthof field.

Besides providing a larger depth of field with two projection distances,the above-described rectangular light pipe shape presents severaladvantages over round light pipes and those of other regular,equilateral shapes. The rectangular shape more closely conforms to theconventional 4:3 horizontal-to-vertical ratio exhibited by commerciallyavailable sensors. The rectangular cross section yields a larger darkfield range than provided by round pipes. It also allows for alower-profile reader, in terms of overall height. Moreover, the use ofdiscrete “sides” on the pipe makes it easier to control separatequadrants, as described above.

Note that, while the embodiments described herein generally contemplatesomewhat polygonal shapes with adjacent sides connected by corners, itis expressly contemplated that continuously curving joints between“sides” can be provided. As such the terms “sides” and pair of opposingsides should be taken to include ellipses in which the opposing sidesspanned by the major axis are greater in length that the opposing sidesspanned by the minor axis. In this manner each set of sides generates anaverage convergence distance for dark field rays that is different,thereby producing the desired enhanced depth of field. To this end, FIG.19 details an elliptical cross section light pipe 1910 that can beadapted for use with an embodiment of the technology (with appropriatereshaping of the illumination ring and diffuser, where applicable. Thedistal end of the light pipe 1910 terminates in a chamfered end 1920having an angle and function as generally described herein. The edge ofthe chamfered end, in essence defines an opposing pair of North andSouth sides (1930 and 1932, respectively) and East and West sides (1940and 1942, respectively), which are separated by distances that differ.In this case the distances are the minor axis MIA and the major axis MAA(respectively) of the ellipse. In this embodiment, the “sides” can becharacterized as continuously running into each other with arbitraryboundaries or with “continuously curving corners.” A variety ofvariations on this basic elliptical shape are expressly contemplated. Inany case, the sides generate at least two discrete distances of rayconvergence for a given fixed chamfer angle.

While at least some of the embodiments described herein generallycontemplate a light pipe configuration with a textured or frostedchamfered distal (forward) end 230 according to the various embodimentsof the technology, the distal end 230 may take on a variety of shapesand surface configurations. For example, FIGS. 20 through 31 show avariety of light transmitters having a distal end 230 that includes avariety of shapes and surface configurations that may be used with thepresent technology to provide one or more of dark field illumination,bright field illumination, and/or diffuse illumination. As non-limitingexamples, the distal end 230 may include a shape or shapes described asflat, rounded, curved, arcuate, angled, grooved, stepped, chamfered,and/or any combination of these and other configurable distal endshapes. In addition, the distal end 230 may include no surfacetreatments or one or more surface treatments. For example, one portionor multiple portions of the distal end 230 may have a surface texture(e.g., polished, frosted), or a surface covering or optical coating(e.g., painted, silver coated, dielectric, mirrored), and may includeadditional materials with optic properties, e.g., opaque materials, oneor more lenses (convex and/or concave) and/or mirrors, and/or anycombination of these and other configurable distal end surfacetreatments, to provide surfaces with diffractive, diffusive, refractive,and/or reflective properties, as non-limiting examples.

To this end, FIG. 20 details an alternative embodiment of the distal end230 of the light pipe 2000. As can be seen, the distal end 230 includestwo generally planar surfaces (although more or less are contemplated,see FIGS. 22 and 27, as non-limiting examples). A bottom surface 2010 isshown to be generally perpendicular, although not required, to theinside surface 2020 of the pipe 2000, and a chamfered surface 2030extends between the bottom surface 2010 and the outside surface 2040.The chamfered surface may be at a predefined angle to the outsidesurface 2040, such as between zero and ninety degrees. In oneembodiment, the bottom surface 2010 may be a diffusive surface, and thechamfered surface 2030 may be a polished surface. The transmitted light2005 may be reflected internally by the chamfered surface 2030 of thelight pipe 2000 to exit bottom surface 2010 and/or inside surface 2020at a low angle as dark field illumination. The light pipe 2000 mayproduce a direct bright field illumination effect along with the darkfield illumination through refraction of some of the transmitted lightthrough either or both the chamfered surface 2030 and the bottom surface2010.

FIG. 21 details an additional alternative embodiment of the distal end230 of the light pipe 2100. As can be seen, the distal end 230 includestwo generally planar surfaces. A first chamfered surface 2110 is shownto be generally perpendicular to and have the same length as, althoughnot required, a second chamfered surface 2130. The first chamferedsurface 2110 extends from the inside surface 2120 of the pipe 2100, andthe second chamfered surface 2130 extends from the outside surface 2140of the light pipe (i.e., the second chamfered surface 2130 extendsbetween the outside surface 2140 and the first chamfered surface 2110).The first chamfered surface 2110 and the second chamfered surface 2130converge at tip 2150. Both the first and second chamfered surfaces maybe at predefined angles to the inside 2120 and outside 2140 surfaces,respectively, such as between zero and ninety degrees. In oneembodiment, the first chamfered surface 2110 may be a diffusive surface,and the second chamfered surface 2130 may be a polished surface. Thetransmitted light 2005 may be reflected internally by the secondchamfered surface 2130 of the light pipe 2100 to exit the firstchamfered surface 2110 at a low angle as dark field illumination. Thelight pipe 2100 may produce a direct bright field illumination effectalong with the dark field illumination through refraction of some of thetransmitted light through either or both the first chamfered surface2110 and the second chamfered surface 2130.

FIG. 22 details an additional alternative embodiment of the distal end230 of the light pipe 2200. As can be seen, the distal end 230 includesthree generally planar surfaces. A bottom surface 2210 is shown to begenerally perpendicular, although not required, to the inside surface2220 of the pipe 2200. A chamfered surface 2230 extends between surface2260 and the outside surface 2240. Surface 2260 is shown to be generallyperpendicular, although not required, to the bottom surface 2210. Thechamfered surface 2230 and surface 2260 converge at tip 2250, andsurface 2260 and bottom surface 2210 converge at corner 2270. Thechamfered surface 2230 may be at predefined angles to the outsidesurface 2240, such as between zero and ninety degrees. In oneembodiment, the bottom surface 2210 may be a diffusive surface, thechamfered surface 2230 may be a polished surface, and surface 2260 maybe a diffusive surface. The transmitted light 2005 may be reflectedinternally by the chamfered surface 2230 of the light pipe 2200 to exitsurface 2260 at a low angle as dark field illumination. The light pipe2200 may produce a direct bright field illumination effect along withthe dark field illumination through refraction of some of thetransmitted light through the chamfered surface 2230, surface 2260,and/or the bottom surface 2210.

FIG. 23 details an additional alternative embodiment of the distal end230 of the light pipe 2300. The distal end 230 is similar inconfiguration to the distal end of light pipe 244 previously describedin that it includes a chamfered surface 2310 extending between theinside surface 2320 and the outside surface 2340. As previouslydescribed, the chamfered surface may be at a predefined angle to theoutside surface 2340, such as between zero and ninety degrees. In oneembodiment, the chamfered surface 2310 may include more than one surfacetreatment. As a non-limiting example, the chamfered surface 2310 mayinclude both a diffusive portion 2312 and a polished portion 2314. Thetransmitted light 2005 may be reflected internally by the polishedportion 2314 of the light pipe 2300 to exit inside surface 2320 at a lowangle as dark field illumination. The light pipe 2300 may produce adirect bright field illumination effect along with the dark fieldillumination through refraction of some of the transmitted light throughthe diffusive portion 2312 and/or the polished portion 2314.

FIG. 24 details yet an additional alternative embodiment of the distalend 230 of the light pipe 2400. As can be seen, the distal end 230includes two surfaces (although more or less are contemplated). A bottomsurface 2410 is shown to be generally arced (i.e., non-planar) andextending from the inside surface 2420 of the pipe 2400. A chamferedsurface 2430 extends between the bottom surface 2410 and the outsidesurface 2440. The chamfered surface may be at a predefined angle to theoutside surface 2440, such as between zero and ninety degrees. In oneembodiment, the bottom surface 2410 may be a diffusive surface, and thechamfered surface 2430 may be a polished surface. The transmitted light2005 may be reflected internally by the chamfered surface 2430 of thelight pipe 2400 to exit bottom surface 2410 and/or inside surface 2420at a low angle as dark field illumination. The light pipe 2400 mayproduce a direct bright field illumination effect along with the darkfield illumination through refraction of some of the transmitted lightthrough either or both the chamfered surface 2430 and the bottom surface2410.

FIG. 25 details an additional alternative embodiment of the distal end230 of the light pipe 2500. The light pipe 2500 may be consideredsimilar to the light pipe 2400 shown in FIG. 24, except that the twosurfaces are generally reverses. As can be seen in FIG. 25, the distalend 230 includes two surfaces (although more or less are contemplated).A chamfered surface 2510 is shown to be generally planar and extendingfrom the inside surface 2520. An arced (i.e., non-planar) surface 2530extends between the chamfered surface 2510 and the outside surface 2540.The chamfered surface may be at a predefined angle to the inside surface2520, such as between zero and ninety degrees. In one embodiment, thechamfered surface 2510 may be a polished surface, and the arced surface2530 may be a diffusive surface. The transmitted light 2005 may bereflected internally by the chamfered surface 2510 of the light pipe2500 to exit inside surface 2520 at a low angle as dark fieldillumination. The light pipe 2500 may produce a direct bright fieldillumination effect along with the dark field illumination throughrefraction of some of the transmitted light through either or both thechamfered surface 2510 and the arced surface 2530.

FIG. 26 details an additional alternative embodiment of the distal end230 of the light pipe 2600. As can be seen, the distal end 230 includesone surface 2610 that is generally curvilinear in shape. The surface2610 can be formed by the convergence of two surfaces at tip 2650. Thetip 2650 can be equidistant between the inside surface 2620 and theoutside surface 2640 of the pipe 2600, or the tip 2650 can be offsetbetween the inside and outside surfaces as shown. In one embodiment, thecurvilinear surface 2610 may include more than one surface treatment. Asa non-limiting example, the curvilinear surface 2610 may include both adiffusive portion 2612 and a polished portion 2614. The transmittedlight 2005 may be reflected internally by the polished portion 2614 ofthe light pipe 2600 to exit the diffusive portion 2612 and/or insidesurface 2620 at a low angle as dark field illumination. The light pipe2600 may produce a direct bright field illumination effect along withthe dark field illumination through refraction of some of thetransmitted light through either or both the diffusive portion 2612 andthe polished portion 2614.

FIG. 27 details still an additional alternative embodiment of the distalend 230 of the light pipe 2700. As can be seen, the distal end 230includes a generally stepped surface 2710 extending between the insidesurface 2720 and the outside surface 2740 of the pipe 2700. As shown,each “step” is of a similar or same length, but varied lengths are alsocontemplated. In addition, each step is shown to have a generallyconsistent angular displacement with adjacent steps. Again, variedangular displacements are also considered. In one embodiment, thestepped surface 2710 may include more than one surface treatment. As anon-limiting example, the stepped surface 2710 may include bothdiffusive steps 2712 and polished steps 2714. The transmitted light 2005may be reflected internally by the polished steps 2714 of the light pipe2700 to exit the diffusive steps 2712 and/or inside surface 2720 at alow angle as dark field illumination. The light pipe 2700 may produce adirect bright field illumination effect along with the dark fieldillumination through refraction of some of the transmitted light througheither or both the diffusive steps 2712 and the polished steps 2714.

FIG. 28 details an additional alternative embodiment of the distal end230 of the light pipe 2800. The light pipe 2800 may be consideredsimilar to the light pipe 2300 shown in FIG. 23, except that the surface2810 may include the addition of one or more materials 2830 with opticproperties, e.g., diffusive, reflective, refractive, and/or lensproperties. Both convex and concave lens varieties are contemplated,including lenses such as a holographic lens. The transmitted light 2005may be reflected internally by the surface 2810 of the light pipe 2800to exit inside surface 2820 at a low angle as dark field illumination.The light pipe 2800 may produce a direct bright field illuminationeffect along with the dark field illumination through refraction of someof the transmitted light through the surface 2810 and the material 2830.It is contemplated that the material 2830 may be a solid layer ofmaterial or may be segmented.

FIG. 29 details an additional alternative embodiment of the distal end230 of the light pipe 2900. As can be seen, the distal end 230 includesthree generally planar surfaces and an extended tip 2950. A bottomsurface 2910 is shown to be generally perpendicular, although notrequired, to the inside surface 2920 of the pipe 2900. Surface 2960 isshown to be generally perpendicular, although not required, to thebottom surface 2910. A chamfered surface 2930 extends between surface2960 and the outside surface 2940. The chamfered surface 2930 may be atpredefined angles to the outside surface 2940, such as between zero andninety degrees. In one embodiment, the extended tip 2950 may be opaqueand the chamfered surface 2930 may be a polished surface. Thetransmitted light 2005 may be reflected internally by the chamferedsurface 2930 of the light pipe 2900 to exit surface 2920 at a low angleas dark field illumination. The light pipe 2200 may produce a directbright field illumination effect along with the dark field illuminationthrough refraction of some of the transmitted light through the extendedtip 2950 and/or the chamfered surface 2930.

FIG. 30 details an additional alternative embodiment of the distal end230 of the light pipe 3000. As can be seen, the distal end 230 includestwo surfaces (although more or less are contemplated). A bottom surface3010 is shown to be generally arced (i.e., non-planar) and extendingfrom the outside surface 3040 of the pipe 3000. A chamfered surface 3030extends between the bottom surface 3010 and the inside surface 3020,although chamfered surface 3030 may also be non-planar. Inside surface3020 may curve or extend inward at 3050 to meet chamfered surface 3030.The chamfered surface may be at a predefined angle to the inside 3020and/or outside surface 3040, such as between zero and ninety degrees. Inone embodiment, the chamfered surface 3030 may be a diffusive surface,and the bottom surface 3010 may be a polished surface. The transmittedlight 2005 may be reflected internally by the bottom surface 3010 of thelight pipe 3000 to exit chamfered surface 3030 and/or inside surface3020 at a low angle as dark field illumination. The light pipe 3000 mayproduce a direct bright field illumination effect along with the darkfield illumination through refraction of some of the transmitted lightthrough either or both the chamfered surface 3030 and the bottom surface3010.

FIG. 31 details an additional alternative embodiment of the distal end230 of the light pipe 3100. As can be seen in the end view, the distalend 230 is staggered to include more than one end configuration. Asshown, the distal end 230 includes staggered flat surfaces 3110 andchamfered surfaces 3130. It is contemplated that the distal end caninclude any number of end configurations, and can include anycombination of the light pipe configurations described herein. It isalso contemplated that the light pipe may comprise shapes other than therectilinear shape as shown. For example, in an end view, the light pipemay be square, triangular, elliptical, curved, ovular, or circular, asnon-limiting examples. The transmitted light 2005 may be reflectedinternally by the chamfered surface 3130 of the light pipe 3100 to exitinternal surface 3120 at a low angle as dark field illumination. Thelight pipe 3100 may produce a direct bright field illumination effectalong with the dark field illumination through refraction of some of thetransmitted light through the flat surfaces 3110 and/or the chamferedsurfaces 3130.

In one embodiment, one or more of the above described surfaces mayinclude a dielectric coating. The application of one or more dielectriccoatings provides the opportunity to “tune” the light pipe so as toallow light of one wavelength to pass or transmit through the coating,and to allow light of a different wavelength to reflect.

In an additional embodiment, one or more diffusive/diffractive materialsmay be applied to any of the above described surfaces. For example,known optical diffusers include ground glass diffusers, Teflondiffusers, holographic diffusers, opal glass diffusers, and greyed glassdiffusers, as non-limiting examples.

It is to be appreciated that the distal end 230 of the light pipesdescribed herein may be a separate component or components that arecoupled to a light pipe, or the distal end may be unitary with the lightpipe. The terms “light transmitter” and “light pipe” are usedinterchangeably and in a non-limiting way, and are meant to define aconfiguration of light transmissive material. Accordingly, a light pipemay consist of only the distal end portion as previously described,i.e., a portion just long enough to provide the desired optical effect,such as bright field and/or dark field illumination, or conversely, alight pipe may comprise a device having a length plus the distal endportion. It is also to be appreciated that the embodiments describedabove are not limited to the surface treatments as described. Forexample, one or more lenses or other materials may be applied over orunder any of the diffusive and/or textured surfaces and/or materialsdescribed, or linear surfaces may be non-linear or stepped (as shown inFIG. 27), or any combination of the above described treatments. It isalso contemplated that the light pipe configurations described above maycomprise one or more individual portions, such as four quadrants asdescribed above, so as to allow different sections to be individuallycontrolled and provide varied illuminating effects based on theapplication and/or desired results. It is also contemplated that thelight pipe configurations described above may comprise one or morenested (e.g., concentric) light pipes, so as to allow individual lightpipes to be individually controlled and provide varied illuminatingeffects based on the application and/or desired results. It should beclear from the above-described embodiments, that a reader havingsuperior illumination and mark-reading capabilities is described herein.This reader alleviates many of the disadvantages encountered with priorart readers, and provides improved object-illumination,status-indication and overall durability.

The foregoing has been a detailed description of illustrativeembodiments of the technology. Various modifications and additions canbe made without departing from the spirit and scope thereof. Forexample, any of the various features described herein can be combinedwith some or all of the other features described herein according toalternate embodiments. Additionally, while a plurality of multicolorLEDs are provided, individual monochromatic LEDs each in a plurality ofcolors can be arranged adjacent to each other on the illumination ringin alternate embodiments. Likewise, while a ring divided into quadrantsis shown, any acceptable division of the overall ring can be providedaccording to alternate embodiments. Certain parts of the overall ringcan be made to work together with other parts according to embodimentshereof. For example, top and right may always work together or top andbottom may always work together. Likewise, additional ring colors, suchas yellow can be employed to provide further types of indicators.Multi-colored illumination sources or a plurality of adjacent individualillumination sources (or combinations of individual and multi-coloredsources) can be used to generate the desired seat of ring colors.Moreover, while a rectangular light pipe is shown and described, agreater range of depth of field may be obtained by providing anon-equilateral shape having more than four sides joined by corners (forexample, an oblique hexagon). This technology contemplates polygonallight pipe cross sections having four or more sides (linear orcurvilinear) joined at corners (that may be rounded). Finally, it isexpressly contemplated that any of the processes or steps describedherein can be implemented as hardware, software, including programinstructions executing on a computer, or a combination of hardware andsoftware. Accordingly, this description is meant to be taken only by wayof example, and not to otherwise limit the scope of this technology.

We claim:
 1. An illumination assembly for a mark reader disposed along an optical viewing axis comprising: a light pipe defined by at least four adjacent sides including a first opposing pair of sides and a second opposing pair of sides, the light pipe including a chamfered edge at a distal end that directs light from a ring light source at the proximal end onto a surface as dark field; and wherein a first spacing between the first opposing pair of the sides has a length different than a length of a second spacing between the second opposing pair of the sides.
 2. The illumination assembly as set forth in claim 1 wherein the first opposing pair of sides and the second opposing pair of sides define collectively an approximate shape of an ellipse.
 3. The illumination assembly as set forth in claim 1 wherein at least one of the first opposing pair of sides and the second opposing pair of sides define curvilinear arcs.
 4. The illumination assembly as set forth in claim 1 wherein both of the first opposing pair of sides and the second opposing pair of sides define curvilinear arcs.
 5. The illumination assembly as set forth in claim 1 wherein the first opposing pair of sides and the second opposing pair of sides collectively define a rectangle having corners between adjacent sides.
 6. The illumination assembly as set forth in claim 5 wherein the corners are rounded.
 7. An illumination assembly for a mark reader disposed along an optical viewing axis comprising: a light pipe defined by at least four sides including at least a first opposing pair of sides and a second opposing pair of sides, the light pipe including a chamfered edge at a distal end that directs light from a light source at the proximal end through the chamfered edge onto a surface as dark field light rays; and wherein the convergence distance of the dark field light rays for the at least first opposing pair of sides is less than the convergence distance of the dark field light rays for the at least second opposing pair of sides.
 8. The illumination assembly as set forth in claim 7 wherein a first spacing between the at least first opposing pair of the sides has a first length different than a second length of a second spacing between the at least second opposing pair of the sides.
 9. The illumination assembly as set forth in claim 7 further including a third opposing pair of sides.
 10. The illumination assembly as set forth in claim 7 where the chamfered edge is an exterior wall at the distal end.
 11. An illumination assembly for a mark reader disposed along an optical viewing axis comprising: a rectangular light pipe defined by a set of linear or non-linear sides that intersect at each of four corners that cause the approximate direction of two adjacent sides to vary by substantially ninety degrees; a light source at a proximal end of the rectangular light pipe to direct light through a distal end of the rectangular light pipe onto a surface as dark field light rays; and wherein the dark field light rays from the set of linear or non-linear sides that intersect at each of four corners converge at at least two differing distance ranges of the dark field light rays onto the surface.
 12. The illumination assembly as set forth in claim 11 wherein the rectangular light pipe includes a chamfered edge at the distal end that directs the light from the light source through an interior edge onto the surface as the dark field light rays.
 13. The illumination assembly as set forth in claim 11 wherein the set of linear or non-linear sides that intersect at each of four corners includes at least four sides including at least a first opposing pair of sides and a second opposing pair of sides.
 14. The illumination assembly as set forth in claim 13 wherein a convergence distance of the dark field light rays for the at least first opposing pair of sides is less than a convergence distance of the dark field light rays for the at least second opposing pair of sides. 